Temperature compensating insert for a mechanically leveraged smart material actuator

Abstract

An apparatus having a smart material actuator, a support structure and at least one temperature compensating material insert, either externally mounted to the support structure, integrally formed with the support structure, or any combination thereof. The apparatus includes a mechanically leveraged electrically stimulated smart material. The support structure and actuator are susceptible to the effects of differences in thermal coefficients of expansion of the materials used in the construction. The smart material typically displaces less than 0.001 inches and is leveraged up to fifty times to obtain useful movement. The temperature effect on the smart material is therefore leveraged and amplified producing undesirable motion in the apparatus with ambient and / or operating temperature changes. A method for dimensioning and placement of a compensating insert with respect to the support structure provides an accurate and cost effective compensating insert.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of provisional patent application No. 60 / 393,799 filed on Jul. 3, 2002, which is incorporated by reference herein.FIELD OF THE INVENTION[0002]The present invention relates to a temperature compensating apparatus for a mechanically leveraged smart material actuator and method for the same.BACKGROUND OF THE INVENTION[0003]Various smart material actuator technologies have been developed for a wide range of applications in different industries. One component used in this type of actuator is an electrically stimulated smart material actuator. These smart material actuators when electrically stimulated change shape. This shape change can be designed such that one axis predominantly changes. Such a smart material actuator can be incorporated within a main support structure. As the axis of the smart material actuator changes dimension its motion is magnified by a lever integral to the main support structure. As ...

AI Technical Summary

Benefits of technology

[0006]An apparatus according to the present invention includes a support structure with first and second arms spaced apart from one another. A smart material actuator, such as a piezoelectric actuator, moves the first and second arms with respect to one another in response to expansion and contraction of the actuator. Means for compensating for the effects of different thermal coefficients of expansion of the materials used in the support structure and actuator is provided to reduce or eliminate movement of the arms resulting from variations in working temperature and / or ambient temperature.

[0007]The present invention provides a simple, cost effective solution for compensating a mechanically leveraged actuator for temperature variations. The present invention provides means for compensating for the effects of different thermal coefficients of expansion while not increasing the envelope of the actuator system, and can correct the overall zero voltage error to no greater than ± seven percent of the maximum movement of the actuator system. As a result of the scalability of the actuator system, a process for the development of all parameters has been developed that reduces the time to design a particular physical configuration of an actuator / support structure combination for use in a specific application. The present invention uses a design system, a smart material actuator, a support structure with integral mechanically leveraged arm portions, and a temperature compensating insert element. The temperature compensating insert element is placed at a predetermined position on the support structure spaced from the actuator, such as along an arm portion. This insert element can be inserted into a cutout in the arm portion. By using two different materials for the insert and the arm portion, a bi-material or bi-metal type of movement cantilevering the arm portion can be created. Therefore, with the use of the design system, the placement, and material type of the temperature compensating insert element become readily apparent using a minimum number of components while maintaining an error band of less then 5 percent of travel.

Problems solved by technology

This method suffers from several problems.

One such problem is the length of the compensating element inserted between the main body and the smart material increases the overall length of the actuator.

This is a difficult combination to achieve with inexpensive materials.

This system uses several parts, all of which are complex, and costly to machine and increases the overall size making it less desirable.

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